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System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

Clarify and agree on the scope of the system

User cases (description of sequences of events that, taken together, lead to a system doing something useful)
- Who is going to use it?
- How are they going to use it?

Don't use VPN services.

No, seriously, don't. You're probably reading this because you've asked what VPN service to use, and this is the answer.

Note: The content in this post does not apply to using VPN for their intended purpose; that is, as a virtual private (internal) network. It only applies to using it as a glorified proxy, which is what every third-party "VPN provider" does.

A Russian translation of this article can be found here, contributed by Timur Demin.
A Turkish translation can be found here, contributed by agyild.
There's also this article about VPN services, which is honestly better written (and has more cat pictures!) than my article.

Complete Recent Discord Quest

Note

This no longer works in browser!

Note

This no longer works if you're alone in vc! Somebody else has to join you!

How to use this script:

Accept the quest under User Settings -> Gift Inventory

Reverse Engineering Webpack Apps

Some notes and techniques for reverse engineering Webpack (and a little bit about React/Vue/Angular) apps.

`:bowtie:`	😄 `:smile:`	😆 `:laughing:`
😊 `:blush:`	😃 `:smiley:`	☺️ `:relaxed:`
😏 `:smirk:`	😍 `:heart_eyes:`	😘 `:kissing_heart:`
😚 `:kissing_closed_eyes:`	😳 `:flushed:`	😌 `:relieved:`
😆 `:satisfied:`	😁 `:grin:`	😉 `:wink:`
😜 `:stuck_out_tongue_winking_eye:`	😝 `:stuck_out_tongue_closed_eyes:`	😀 `:grinning:`
😗 `:kissing:`	😙 `:kissing_smiling_eyes:`	😛 `:stuck_out_tongue:`

Setup Postgresql

run postgresql with systemctl

Install postgres

latest

sudo pacman -S postgresql

specific version

find version & build from source

Modified Preorder Tree Traversal

Hierarchical data metrics that allows fast read operations on tree like structures.

Based on Left and Right fields that are set during tree traversal. When entered into node value is set to it's Left, when exiting node value is set to it's Right.

Sample implementation

	'use strict'

	const web3 = require('@solana/web3.js')
	const splToken = require('@solana/spl-token')
	const bs = require('bs58')

	const connection = new web3.Connection(
	web3.clusterApiUrl('devnet'),
	'confirmed',
	)

	#!/usr/bin/env python

	# Linux usage: ./extract_tampermonkey_script.py "/home/<USER>/.config/<BROWSER>/Default/Local Extension Settings/<EXTENSION_ID>"
	# i.e.: ./extract_tampermonkey_script.py "/home/foo/.config/google-chrome-beta/Default/Local Extension Settings/gcalenpjmijncebpfijmoaglllgpjagf"
	# Mac usage: ./extract_tampermonkey_script.py "/Users/<USER>/Library/Application Support/Google/Chrome/Default/Local Extension Settings/<EXTENSION_ID>/"
	# i.e.: ./extract_tampermonkey_script.py "/Users/foo/Library/Application Support/Google/Chrome/Default/Local Extension Settings/dhdgffkkebhmkfjojejmpbldmpobfkfo/"

	import leveldb
	import sys
	import re

	#!/usr/bin/python
	#
	# Pickle deserialization RCE payload.
	# To be invoked with command to execute at it's first parameter.
	# Otherwise, the default one will be used.
	#

	import cPickle
	import sys
	import base64